1. Field of the Invention
The present invention relates to systems and methods for detecting and classifying particles through optical means.
2. Background of the Invention
It has been a longstanding desire to provide systems and methods for accurately detecting particle size, quantities, and whether the particles are biological or not. The detection and categorization of biological particles, in particular, is generally referred to as cytometry. Accurate and portable cytometry equipment is presently of critical importance to detect biological pathogens, such as anthrax, or other pathogens that may impact public health.
Known cytometry methodologies make use of fluorescence, often initiated by laser light, to identify particles. In this particular methodology, a laser wavelength is selected to be near or at the peak of an absorption resonance in the particle, trace gas, compound or chemical element to be detected. This absorption resonance is selected to be one that causes strong fluorescence. In one such known cytometry system, described in U.S. Pat. No. 4,651,010 to Javan, laser light illuminates air drawn through a duct, which may bear the particles to be detected, such light having a wavelength near or at the peak of an absorption resonance in the trace gases or chemical elements to be detected. A photodetector responds to the resulting radiation of fluorescent light caused by the laser induced biochemical fluorescence. As mentioned in the patent to Javan, it is also known to pulse the illuminating laser beam and gate the receiver coupled to the photodetector to cause it to respond in a delayed manner during a short period following each laser illumination pulse. The delay is fashioned to take advantage of the fluorescence decay time of the agent to be detected, so as to discriminate against false ambient illumination.
In addition to fluorescence techniques, particle geometry can be characterized by illuminating the particles with an excitation source and recording the scattering profiles. Such a system is described in U.S. Pat. No. 5,561,515 to Hairston et al.
Despite the availability of advanced apparatuses in the field of particle detection & classification, such as those described in the patents to Javan and Hairston et al., there is nevertheless a need for improved systems and methods.